A system of vectors for Bacillus subtilis spore surface display

BACKGROUND Bacterial spores have been utilized as platforms for protein display. The best studied display systems are based on Bacillus subtilis spores in which several coat proteins have successfully been used as anchors for heterologous protein. Increasing knowledge about spore coat structure enables selection of new anchor proteins such as CotZ and CgeA. Here we describe a system of vectors for display of proteins on the surface of B. subtilis spores. RESULTS We have designed and constructed a set of 16 vectors for ectopic integration which can be used for spore surface display of heterologous proteins. There is a selection of five coat proteins: CotB, CotC, CotG, CotZ and CgeA which can be used for construction of fusions. Three of these (CotB, CotC and CotG) enable obtaining N-terminal and C-terminal fusions and other two (CotZ and CgeA) are designed to produce C-terminal fusions only. All the vectors enable introduction of an additional peptide linker between anchor and displayed protein to enhance surface display. As a selection marker trophic genes are used. Additionally we describe an example application of presented vector system to display CagA protein of Helicobacter pylori in fusion with CgeA spore coat protein. CONCLUSIONS Described system of vectors is a versatile tool for display of heterologous proteins on the surface of B. subtilis spores. Such recombinant spores can be further used as for example biocatalysts or antigen-carriers in vaccine formulations. The lack of antibiotic resistance genes in the system makes such spores an interesting option for applications in which a possible release to the environment can occur.